1. Field of the Invention
The present invention relates to a bone reinforcing agent and food and drink products containing the same, exhibiting a bone reinforcing activity. Because the bone reinforcing agent and the food and drink products containing the same of the present invention exhibit the effects of promoting the growth of osteoblasts and suppressing bone resorption by osteoblasts, they are useful in treating or preventing various bone diseases such as osteoporosis, bone fractures, rheumatism, and arthritis.
2. Description of the Background Art
In recent years, the incidence of bone diseases such as osteoporosis, bone fractures, lumbago, and the like, have increased along with the progressive increase in the elderly population. These diseases are caused by insufficient calcium intake, decreased calcium absorption hormonal imbalance postmenopause, and the like. Increasing the peak bone mass, or the total amount of bone in the body, is considered to be effective in preventing bone diseases such as osteoporosis, bone fractures, lumbago, and the like in aged people. Increasing the peak bone mass is equivalent to strengthening the bone. Controlling bone resorption is also considered to be effective in preventing osteoporosis. Bone synthesis is characterized by a repeated balanced formation-resorption cycle which is called remodeling. Hormonal imbalance postmenopause causes bone resorption to predominate over bone formation, resulting in osteoporosis. Accordingly, bones are reinforced by controlling bone resorption and maintaining bone mass at a certain level.
Various calcium agents, such as calcium salts (e.g. calcium carbonate, calcium lactate or calcium phosphate), milk or whey calcium, and natural calcium agents (e.g. cattle bone meal or egg shell), and the like, are used to strengthen the bones. These agents are individually administered or added to foods or drinks together with other additives, such as casein phosphopeptide which have the effect of increasing calcium absorption. However, more than half of the calcium salts and natural calcium administered are said to be excreted without being absorbed by the body. Even if absorbed, calcium may not necessarily be utilized for the improvement of bone metabolism or for the reinforcement of bones because the affinity of calcium for bone differs according to the form of the calcium and types of other nutrients which are taken together with calcium. Vitamin D.sub.3, calcitonin preparations, estrogen preparations, and the like are known as treatments for osteoporosis or reinforcing bones. In addition, new drugs such as bisphosphonate preparations are under development. Administration of these drugs, however, may be accompanied by side effects such as ear noises, headache, and anorexia. Furthermore, the addition of these drugs to food or drink is currently infeasible due to safety, and cost considerations. Therefore, the development of a bone reinforcing agent, or a food or drink product containing a bone reinforcing agent, which can be orally administered over an extended period of time and which directly exhibits the bone growth promoting effect or the bone resorption suppressing effect, and is effective in the treatment or prevention of the osteoporosis, is desirable.
In view of the above-mentioned problems, the present inventors have undertaken extensive research into the substances contained in various raw food materials which exhibit a bone reinforcing effect. This research has resulted in the finding that a basic protein fraction derived from milk or basic peptide fractions obtained by hydrolyzing the basic protein fraction with a protease, such as pepsin or pancreatin, exhibit the effects of promoting growth of osteoblasts and suppressing resorption of osteoclasts, and can strengthen bone when administered orally. The inventors of the present invention have found that the basic protein fractions and the basic peptide fraction can be used as a bone reinforcing agent or as an effective component for bone reinforcing food and drinks. These findings have led to the present invention.